If I have an ACL, when applying it to an interface, I need to say "in" or "out". Is "in" referring to where the traffic is FROM, or where it is going TO?

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    You should also look carefully at the placement. In general, standard ACLs should be placed as close the the destination as possible, while extended ACLs should be placed as close to the source as possible.
    – Ron Maupin
    Jul 18, 2016 at 17:15
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    – Ron Maupin
    Aug 14, 2017 at 21:19

1 Answer 1


The terms IN and OUT are in reference to the router interface. So IN means traffic coming into the router from that interface. OUT means traffic leaving the router interface.

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